1.Field
This invention concerns improvements relating to velocity extraction in the field of radiation pulse echo detection. More particularly but not exclusively, this invention concerns extraction of the velocity of a target from the returns.
2.Related Art
Radiation pulse echo detection systems, such as radar, transmit a set of one or more coherent strings of pulses (coherent bursts) which are reflected by objects. The echoes of pulses are used to detect and locate distant objects.
Conventionally, a surveillance radar would estimate the target radial velocity using multiple estimates of the target range taken at different times. It is now common practice to filter the returns to remove clutter returns (those returns from items not of interest), leaving any returns from moving items of interest relatively unaffected. This is known as Moving Target Detection (MTD) or Moving Target Indication (MTI). Such schemes can be modified using multiple filters to obtain some measure of target radial velocity but suffer from problems due to large clutter returns ‘spilling’ into adjacent filters, thereby producing erroneous velocity measurements.
One of the main tasks of modern radars and sonars, is to identify and track moving targets. The accuracy of tracking is greatly enhanced if the range ambiguity and radial velocity of the target input plots are known. Only plots with matching range ambiguity and velocity will then be associated with those from previous measurements thereby significantly reducing the probability of mis-association, track seduction and false track rate.
Whilst traditional filtering methods remove the clutter from the in-phase (I) and quadrature (Q) components (the first being in phase with the transmitted signal and the second in quadrature with the transmitted signal) and typically return the target amplitude, they do not easily output the target radial velocity nor the range ambiguity of the target.